1. Field of the Invention
The present invention relates to a substrate polishing apparatus and method, and more particularly to a substrate polishing apparatus and method suitable for polishing an insulating material layer or a conductive material layer on a large-size glass substrate. Further, the present invention relates to a substrate receiving method.
2. Description of the Related Art
Transparent glass substrates for use in solar cells and flat displays have circuits formed thereon using silver paste by printing. However, the process of using silver paste has been problematic in that such a process is highly costly and experiences difficulty in producing fine interconnections.
As image display apparatuses typified by liquid crystal displays have become larger in size, glass substrates used therein also have become larger in size. For producing fine interconnections for those larger image display apparatuses and reducing the cost of them, there have been demands for an interconnection forming process in which, instead of using carbon paste and silver paste, an insulating layer is deposited on a glass substrate, fine interconnection grooves are formed in the surface of the insulating layer, a plated metal layer (e.g., a plated Cu layer) is embedded in the interconnection grooves, and any extra metal layer is removed to provide a flat surface.
One conventional technology for achieving high surface planarization is the process of polishing wafers (substrates) for fabricating semiconductor devices. Generally, a CMP (Chemical Mechanical Polishing) apparatus is known in the art as an apparatus for polishing wafers. The CMP apparatus comprises a vertical rotatable shaft, a substrate holder mounted on the lower end of the vertical rotatable shaft for holding a substrate with its surface to be polished facing down, another vertical rotatable shaft, a turntable mounted on the upper end of the other vertical rotating shaft facing the substrate holder, and a polishing pad attached to the upper surface of the turntable. In the CMP apparatus, the substrate held by the rotating substrate holder is pressed against the polishing pad on the rotating turntable to polish the substrate. Simultaneously, a polishing liquid such as a slurry, or the like, is used to cause a chemical reaction for polishing the substrate. For details, reference should be made to Japanese laid-open patent publication No. 2003-309089.
If glass substrates to be polished by the CMP apparatus become larger in size, then the CMP apparatus needs to become also larger in size. For making the CMP apparatus higher in functionality and more compact, it is necessary to solve the following problems:
(1) A large-size glass substrate needs to be reliably held against and attracted to the holding surface (flat surface) of the substrate holder. However, a large-size glass substrate is thin and highly liable to be deformed or bent. Furthermore, a glass substrate which is plated with copper or the like before it is polished tends to be warped and is highly likely to break. Such a tendency has to be held to a minimum.
(2) If particles and foreign matter are trapped between the holding surface of the substrate holder and the surface of the glass substrate, then the glass substrate tends to be broken while it is being polished. Therefore, it is necessary to prevent particles and foreign matter from being trapped between the holding surface of the substrate holder and the surface of the glass substrate.
(3) When a large-size glass substrate is polished, the polishing pad on the upper surface of the turntable and the glass substrate have large contact areas, respectively, and produce a large amount of frictional heat. A large amount of heat is also produced by the chemical reaction of the slurry (polishing liquid), or the like. These amounts of heat have to be lowered.
(4) A large amount of slurry (polishing liquid) is required to polish a large-size glass substrate. For reducing the cost of the process of polishing the glass substrate, it is necessary to reduce the amount of the slurry (polishing liquid) which is consumed in the polishing process.
(5) The large-size glass substrate is attracted by the substrate holder through an attracting surface (holding surface) of the substrate holder which has a large attracting area, and is held in close contact with the attracting surface under surface tension. After the glass substrate is polished, therefore, the glass substrate is highly difficult to release (remove) in its entirety from the attracting surface in one direction under uniform forces, and may possibly be damaged when it is removed from the substrate holder. It is necessary to release (remove) the glass substrate from the attracting surface of the substrate holder without causing damage to the glass substrate.
(6) The CMP apparatus requires a large-size cleaning unit for cleaning the large-size glass substrate which has been polished. Generally, the CMP apparatus has a glass substrate transfer unit such as a robot for transferring the glass substrate to the cleaning unit after the glass substrate is polished. However, the glass substrate transfer unit for transferring a large-size glass substrate makes it difficult to make the CMP apparatus more compact and less costly.
(7) The polishing pad attached to the upper surface of the turntable is a consumable product that needs to be replaced after it has reached the end of its service life. However, the polishing pad on the large-size turntable cannot easily be replaced in a short period of time. Therefore, it is necessary to facilitate replacement of the polishing pad for shortening machine downtime.